This invention is generally directed to liquid printing processes, and, more specifically, the present invention relates to coating substrates, such as papers, like Xerox Corporation 4024 papers, for use in liquid printing processes. This invention provides in embodiments materials and methods for coating the side of a substrate to which a liquid toner image is to be transferred. The coating may be accomplished before the paper is loaded into an imaging apparatus, such as a printer/copier, or the coating may be performed in the apparatus prior to transfer of the image. This invention in embodiments provides for excellent liquid toner transfer, which transfer is improved with respect to transfer wherein the final substrate is not coated. More specifically, the present invention relates to processes wherein improved image transfer is achievable to coated papers after development of an image on an imaging member, such as a photoreceptor, reference for example U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference, with, for example, positively charged liquid developers comprised of, for example, thermoplastic resin, colorant, such as pigment, charge control agent, nonpolar liquid, and a charge director of, for example, organic aluminum complexes, or mixtures thereof of the following formulas ##STR2## wherein R.sub.1 is selected from the group consisting of hydrogen and alkyl; wherein alkyl, for example, contains from 1 to about 12 carbon atoms, and n represents a number, such as 1, 2, 3, or 4; and wherein the preferred aluminum complex in embodiments is an aluminum-di-tertiary-butyl salicylate, abbreviated as Alohas.
For image quality, solid area coverage and resolution of developed images there is usually desired, for example, sufficient toner particle electrophoretic mobility. The mobility for effective image development is primarily dependent on the imaging system used, and this electrophoretic mobility is directly proportional to the charge on the toner particles effected by the charge director selected, and inversely proportional to the viscosity of the liquid developer fluid. For example, an about 10 to 30 percent change in fluid viscosity caused for instance by an about 5.degree. C. to 15.degree. C. decrease in temperature could result in a decrease in image quality, poor or unacceptable image development and undesirable image background development, for example, because of a 5 percent to 23 percent decrease in electrophoretic mobility. Insufficient particle charge and the use of uncoated substrates, such as paper, can result in poor, or ineffective transfer of the developer or toner to paper, or other substrates. With liquid developer materials, such as those described in the copending applications referenced herein, absorption of carrier liquid into a rough and/or absorbing final substrate can also result in poor, or ineffective transfer. Poor transfer can, for example, result in poor image solid area coverage if insufficient toner is transferred to the final substrate and can also result in image defects such as smearing and hollowed fine features. To overcome or minimize such problems, the processes of the present invention were arrived at after substantial research efforts, and which processes permit excellent image transfer of, for example, from about 80 to about 98 percent in embodiments.